The present invention relates to photographic flash dischargers, and particularly to a test flash device in which the duration of light emission of a flash discharge tube during test flashing prior to flash photographing is sufficiently short to minimize consumption of energy which is stored in the main discharge capacitor, and thereby to minimize the time required for recharging that capacitor.
Many prior art flash dischargers have automatic light regulators. With these flash dischargers, the quantity of light to be emitted is automatically controlled in accordance with the light reflected on an object to be photographed. Troublesome operation, for example, eye measurement of the distance of the object to be photographed as well as calculation of the diaphragm value based on the object distance may be advantageously eliminated. However, when the object to be photographed is a relatively long distance away, it sometimes occurs that the shutter is released without knowing there is a deficiency of illumination on the object. This occurs when eye measurement of the distance of the object is not performed in preparation for flash photographing and results in an unsatisfactory photograph.
Some known flash dischargers further include a photometric circuit which comprises an integration capacitor and a light emission stopping circuit as the automatic light regulating device. The photometric circuit is exposed to light reflected by the object to be photographed and photoelectrically converts this light to a signal which is integrated by the capacitor. The light emission stopping circuit is activated in response to a signal generated when the integration value of said capacitor has attained a predetermined level.
It has been proposed to provide a display device adapted to present a change in display which is operatively associated with the automatic light regulating device which will indicate that the automatic light regulating device is activated and that the object to be photographed is adequately illuminated even when the object is a long distance away. In these known flash dischargers, test flashing is performed prior to flash photographing and the display device is observed. When a change in display is observed, flash photographing can be performed. When no change in display occurs, the camera diaphragm is regulated to obtain a larger aperture and/or the camera is brought closer to the object to be photographed before another test flash is performed. Flash photographing can be performed only after a change in display is observed.
It will be understood that the flash dischargers described above help determine proper illumination of an object to be photographed prior to actual flash photographing and advantageously reduce the possibility of failure in flash photography even when the object is relatively far away. However, test flashing is performed prior to flash photography and largely consumes the energy stored in the main discharge capacitor. Thus, many known flash dischargers are disadvantageous in that they make it impossible to achieve flash photographing immediately after test flashing.
Specifically, test flashing to determine proper illumination of the object to be photographed when the object is a relatively long distance away requires a correspondingly large quantity of light to be emitted which results in substantial consumption of the energy stored in the main discharge capacitor. Accordingly, flash photographing cannot be performed until the main discharge capacitor is adequately recharged.
Such a restriction that actual photographing cannot be performed until the main discharge capacitor is adequately recharged presents a serious inconvenience for practical use. Even if test flashing indicates that an object to be photographed is sufficiently illuminated, it may occur that the object to be photographed moves during recharging of the main discharge capacitor causing a deficiency of illumination at the time actual flash photographing is performed.